The purpose of this study is the identification of predictors of stable conduct problems in young children. Existing research indicates that antisocial patterns in youth and adults are associated with a history of early childhood behavior problems, but prospective research indicates that only some difficult young children develop antisocial patterns and related psychiatric disorders. This study follows a sample of children who vary in the level of preschool age behavior problems they demonstrate, assessing the children during the preschool years (ages 4-5) and again during the completion of the first year of elementary school (ages 6-7). Dispositional and family correlates of antisocial patterns, particularly the development of regulation of angry and aggressive impulses, are assessed. Observational, psychophysiological, biochemical, cognitive, and sociocognitive data are collected. The findings will yield information for (1) profiling children at-risk for chronic behavior problems, and (2) identifying factors which deter or promote continuity of problems.